3种检测方法在中缅边境疟疾无症状感染者筛查中的比较

Performance comparison of three methods in detecting asymptomatic malaria infection on China-Myanmar border

目的比较3种不同检测方法对疟疾无症状感染者的检出能力,并了解中缅边境地区的疟疾无症状感染水平。方法2014年7月在中缅边境地区云南省盈江县选择那邦镇、支那乡和缅甸拉咱安置点等3个调查点,采集调查对象血样,制作厚薄血膜和滤纸血标本,分别采用显微镜观察、荧光定量PCR和超敏PCR检测疟原虫感染情况。结果共采集387份血样,显微镜观察检出6例无症状感染者(间日疟5例、恶性疟1例),感染检出率为1.6%;荧光定量PCR检出13例无症状感染者(间日疟12例、恶性疟1例),感染检出率为3.4%;超敏PCR检出38例无症状感染者(间日疟29例、恶性疟9例),感染检出率为9.8%。以显微镜观察为疟原虫感染诊断的金标准,荧光定量PCR检测无症状感染者的灵敏度为100%,特异性为98.2%;超敏PCR检测无症状感染者的灵敏度为100%,特异性91.6%。超敏PCR结果显示,那邦镇的无症状感染检出率最高,为17.1%(22/129),其次为缅甸拉咱难民安置点,为10.0%(11/110),支那乡最低,为3.4%(5/148),3个调查点的感染检出率差异有统计学意义(P<0.05)。检出虫种以间日疟原虫为主,占76.3%,恶性疟原虫占23.7%;女性无症状感染检出率为10.7%(23/215),高于男性的8.7%(15/172),两者差异无统计学意义(P>0.05)。不同年龄组以15~29岁的无症状感染检出率最高,为17.5%(10/57),各年龄组间差异无统计学意义(P>0.05)。结论超敏PCR对疟疾无症状感染者的检出率高于荧光定量PCR和显微镜观察。中缅边境地区人群中存在一定比例的疟疾无症状感染者。

Objective To compare the performances of three methods in detecting asymptomatic malaria infection in residents,and assess the prevalence of asymptomatic malaria on China-Myanmar border.Methods Crosssectional survey was carried out in Nabang town and Zhina town in Yingjiang county of Yunnan Province,China and a resettlement site in Laiza of Myanmar.Finger-prick blood samples were collected to prepare thick/thin blood smears and dried blood spots on filter paper.Malaria parasite infection was examined by light microscopy,real-time fluorescent PCR and ultrasensitive PCR(usPCR).Results A total of 387 blood samples were collected.Light microscopy found 6 participants with asymptomatic malaria infection(5 Plasmodium vivax infection and 1 P.falciparum infection),with a detection rate of 1.6%;real-time fluorescent PCR revealed 13 asymptomatic malaria infection cases(12 P.vivax infection;1 P.falciparum infection)with a detection rate of 3.4%;and usPCR found 38 asymptomatic malaria infection cases(29 P.vivax infection and 9 P.falciparum infection)with a detection rate of 9.8%.Using light microscopy as the gold standard,the sensitivity and specificity of real-time fluorescent PCR were 98.2%and100%,and those of usPCR were 91.6%and 100%,respectively.The usPCR results revealed that the detection rate of asymptomatic malaria infections was highest in Nabang town(17.1%,22/129),followed by the Laiza resettlement site(10.0%,11/110)and Zhina town(3.4%,5/148),showing significant differences between the three sites(P<0.05).Among the parasite species detected,P.vivax accounts for 76.3%,while P.falciparum for 23.7%.The detection rate was higher in females(10.7%,23/215)than in males(8.7%,15/172),but with no significant difference(P>0.05).The age distribution showed that,the detection rate of asymptomatic infection was highest in the examinees aged 15-29 years(17.5%,10/57),but there were no significant differences between the age groups.Conclusion Of the three methods compared for the ability in detection of asymptomatic malaria infection,the usPCR method presents higher detection rate than light microscopy and real-time fluorescent PCR.There are a certain proportion of asymptomatic malaria infection cases among the residents on China-Myanmar border.